If standard reduction potential (E^0) of ( Al^ +3 _ (aq) ,| , Al_ (s) ), ( Fe^ +2 _ (aq) ,| , Fe_ (s) ), ( Cu^ +2 _ (aq) ,| , Cu_ (s) ) and ( Ag^ +1 _ (aq) ,| , Ag_ (s) ) are - 1.66 V, - 0.44 V, + 0.34 V and +0.79 V respectively. Which of the following reaction is non spontaneous ?

MHT CET 2026 Chemistry question

If standard reduction potential () of \left(\mathrm{Al^{+3}_{(aq)}}\,|\,\mathrm{Al_{(s)}}\right),\left(\mathrm{Fe^{+2}_{(aq)}}\,|\,\mathrm{Fe_{(s)}}\right),\left(\mathrm{Cu^{+2}_{(aq)}}\,|\,\mathrm{Cu_{(s)}}\right) and are - 1.66 V, - 0.44 V, + 0.34 V and +0.79 V respectively. Which of the following reaction is non spontaneous ?

(A)2\mathrm{Ag_{(s)}} + \mathrm{Fe^{+3}_{(aq)}} \longrightarrow 2\mathrm{Ag^{+1}_{(aq)}} + \mathrm{Fe_{(s)}}Correct
(B)2\mathrm{Al_{(s)}} + 3\mathrm{Cu^{+2}_{(aq)}} \longrightarrow 2\mathrm{Al^{+3}_{(aq)}} + 3\mathrm{Cu_{(s)}}
(C)\mathrm{Fe_{(s)}} + \mathrm{Cu^{+2}_{(aq)}} \longrightarrow \mathrm{Fe^{+2}_{(aq)}} + \mathrm{Cu_{(s)}}
(D)2\mathrm{Al_{(s)}} + 3\mathrm{Fe^{+2}_{(aq)}} \longrightarrow 2\mathrm{Al^{+3}_{(aq)}} + 3\mathrm{Fe_{(s)}}

Answer: (A)

Solution

A reaction is spontaneous if (reduction potentials). (A) Ag is oxidised (anode, +0.79 V) and iron ion is reduced to Fe (cathode, V): V , non-spontaneous. (B) Cathode Cu (+0.34), anode Al (): V, spontaneous. (C)

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Question ID VK-099978